1. Field of the Invention
The present invention relates to polyaminobisimide resins, more particularly, to resins that use particular diamines that are capable of improving the physical properties of the cured products of the resins.
Polyaminobisimide resins are resins having high heat stability which are formed of unsaturated bisimides and diamines.
2. Discussion of Prior Art
Industrially, polyaminobisimide resins are commonly produced by using as an unsaturated bisimide the bismaleimide composed of maleic anhydride and methylenedianiline (MDA; also referred to as methylenebisaniline or 4,4'-diaminodiphenylmethane), and methylenedianiline as a diamine. After being cured to provide a three-dimensional structure, such resins exhibit superior heat stability by resisting thermal distortion. However, they incur such defects as brittleness and insufficient bonding strength which are evidenced by insufficient tensile strength and impact strength, and these defects are believed to originate from the excessive rigidity of the resins.
The physical properties that are required of the cured products of resin compositions to be used in laminates include not only good mechanical properties and high heat stability but also improved ply separation strength and copper foil bonding strength, as well as reduced water absorption. Reduction in water absorption is a particularly important objective since a smaller amount of water absorption will contribute higher reliability to electrical characteristics.